High intensity discharge (HID) lamps are increasingly being used in a wide variety of applications due to their greater efficiency, lower power requirements, and higher light outputs as compared to incandescent lights.
However, the starting and operation of HID lamps require substantially more control over the power to the lamp than is required by incandescent lamps. More particularly, HID lamps typically require a voltage pulse to start or strike the lamp that is significantly higher than the operating voltage across the lamp and the input line voltage. A ballast having a triggering mechanism is typically used to provide such a strike pulse.
There are many known ballasts using a variety of triggering mechanisms. These prior art triggering mechanisms are often ineffective, unreliable, or unduly complicated. Since HID lamps are often used in applications that require a high degree of confidence that the lamp will be reliably struck, such as for security and street lights, it is highly desirable to provide a HID light that will be turned on in a consistent, predictable fashion.
Also, HID lamps are often used in relatively inaccessible locations, such as on tall light poles or attached to the sides or ceilings of large buildings. It is desirable to provide a HID lamp that will start and operate reliably in such applications due to the difficulty of repairing a light fixture in such locations.